Light deflection phenomena in antiferroelectric liquid crystals

Characteristic light deflection phenomena in antiferroelectric chiral smectic liquid crystals were investigated. Strong deflected light beams were observed in parallel alignment cells in the antiferroelectric phase at the electric field induced phase transition to ferroelectric state. The origin of the light deflection phenomenon was confirmed not to be diffraction due to a periodical change of refractive index caused by helical structure which is common to chiral smectic liquid crystals, but to be reflection and refraction at boundaries between coexisting phases or domains. Incident angle dependence of the angle of deflection was numerically analyzed on the basis of the method applied to the case of ferroelastic crystals, and a qualitative agreement between the calculated results and the experimental ones was obtained. Similar light deflection phenomena were observed also in ferroelectric phase and ferrielectric one at zero electric field. Molecular alignment structure in those phase or domains are discussed.